In recent years, there has been an increase in the number of communication terminals, e.g., PDA (Personal Digital Assistants), cellular phones, or personal computers, which are capable of performing various functions via wireless communications, e.g., internet connection, LAN (Local Area Network) access, exchange of business card data, telephone calling, music reproduction, and the like. Although a communication terminal having such a multiplicity of functions is primarily intended to execute a single function at one time, it is also capable of simultaneously executing a plurality of functions. For example, one master communication terminal may simultaneously execute a plurality of functions between itself and a plurality of slave communication terminals.
However, when a plurality of functions are simultaneously executed, a master communication terminal will consume more power than in the traditional case of performing only one function because the master communication terminal needs to perform a communication with each slave communication terminal in order to realize each function. Therefore, a master communication terminal is usually arranged so as to minimize its power consumption, in order to maximize its battery life, for example.
Hereinafter, a commonly-used power save processing method which is performed in a conventional master communication terminal will be described. FIG. 23 is a block diagram illustrating a schematic structure of a conventional master communication terminal. In FIG. 23, the conventional master communication terminal comprises a user input section 110, a link management section 120, a communication processing section 130, a wireless communication section 140, and a specific function processing section 150. The link management section 120 includes a communication link management section 121, a communication link control section 122, and a power save operation control section 123.
The user input section 110 receives an instruction concerning a function of the master communication terminal (e.g., begin data transfer, establish a communication link, a power save command, etc.) from a user or an upper-class application. A request to establish a communication link and a power save command are passed to the link management section 120. Any other instruction is passed to the specific function processing section 150.
Based on predetermined information, the communication link management section 121 determines whether a communication link can be established with a slave communication terminal (based on the request to establish a communication link). If it is determined that the communication link can be established, the communication link management section 121 issues to the communication link control section 122 an instruction to establish a communication link. Upon receiving an instruction to establish a communication link from the communication link management section 121, the communication link control section 122 establishes a communication link with the relevant slave communication terminal by means of the communication processing section 130 and the wireless communication section 140. In accordance with a power save command from the user input section 110, the power save operation control section 123 issues to the communication link management section 121 a request for a transition of an already-established communication link to a power save mode (using a communication cycle as designated by the power save command), and instructs the corresponding slave communication terminal to transition to a power save mode, by using the communication processing section 130 and the wireless communication section 140. The power save command is issued with respect to each slave communication terminal with which a communication link has been established. The power save command contains an instruction to perform power save operation, an instruction concerning the communication cycle of communication links in the power save mode operation, and the like.
The communication processing section 130 performs processes such as a process of establishing a communication link, a process of instructing a transition to the power save mode, and a process instructed by the specific function processing section 150. The wireless communication section 140 carries out a wireless communication with a slave communication terminal. The specific function processing section 150 is a section which processes functions that are specific to the communication terminal.
In the conventional master communication terminal having the above-described structure, power saving is ensured by placing the hardware in a power save state during periods corresponding to unused communication slots, i.e., communication slots other than those used by communication links which have been established by the communication link management section 121 and the communication link control section 122 (FIG. 24). As exemplary operations to be performed during a power save state, the communication terminal may be turned off or clocked down, thereby minimizing the power consumption by hardware elements such as the CPU or peripheral devices.
A technique concerning a power save processing method which is applicable to a wireless communication system comprising an intermittent operation type mobile station, a constant operation type mobile station, and a base station is disclosed in Japanese Patent Laid-Open Publication No. 9-162798. In this technique, the base station gives priority to the data transmission/reception schedule with the intermittent operation type mobile station, thereby providing for an improved throughput and power conservation at the mobile station.
As described above, in accordance with the conventional master communication terminal, the communication cycle and the communication slot used by the communication link management section 121 and the communication link control section 122 for the communication link are arbitrarily fixed every time a request to transition to a power save mode is made. Therefore, unused slots may emerge in small, dispersed units (see FIG. 24).
On the other hand, in order to allow the hardware to transition from a normal state to a power save state or vice versa, a predetermined transition time must be observed.
Therefore, as shown in FIG. 25, in accordance with a power save operation of a conventional master communication terminal where the communication links with all slave communication terminals are allowed to transition to a power save mode, the dispersed existence of unused slots will result in a large total amount of transition time (illustrated by thin lines) being experienced, which effectively reduces the total amount of time (illustrated by thick lines) for the hardware to actually operate in a power save mode.
In the conventional technique disclosed in the aforementioned laid-open patent publication, the base station gives priority to the data transmission/reception schedule with the intermittent operation type mobile station in order to realize power conservation at the intermittent operation type mobile station. However, this technique does not envisage a power save operation at the base station in the case where a plurality of intermittent operation type mobile stations are connected.
Thus, an object of the present invention is to provide a method of reducing the transition time to provide an increased power save operation time for the hardware of a master communication terminal capable of concurrently establishing communication links with a plurality of slave communication terminals, a program for executing the method, and a recording medium containing the program.